Easily displaceable bottom tenser

ABSTRACT

A bottom tenser utilized for a drafting means of a spinning frame, especially for fasciated yarn spinning, in which a fiber bundle is attenuated at a high speed exceeding 100 m/min. The bottom tenser as well as a bottom roller corresponding to the tenser is provided with a free end through which an apron is easily removable from and mountable on the tenser and the roller. The tenser may be constituted by a body and at least a guide wall movable relative to the body. The guide wall prevents lateral movement of the apron in its operative position and, in turn, is displaced or removed from the body in its non-operative position so as not to obstruct an apron exchanging operation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel drafting means for a fiber bundle. More specifically, it relates to a bottom tenser for tensioning an apron around a bottom roller of a high speed drafting means.

2. Description of the Prior Art

Recently, the processing speeds of spinning frames have been significantly increased. In fasciated yarn spinning, in which a fiber bundle attenuated by a drafting means is false-twisted in an air nozzle, processing speeds of 100 m/min, in some cases, 200 m/min, have been attained by actual machines.

Under such high processing speeds, however, more troubles occur in the drafting means compared to speeds of under 20 m/min, the maximum rate for conventional ring spinning frames. One of the most serious problems accompanying high speed drafting is damage of aprons wrapped around a middle roller for nipping the fiber bundle. In this regard, according to the present inventors' experience, most of the aprons provided on a high speed spinning frame wear out or break down after a one-month run. Therefore, it is essential to replace aprons periodically to ensure continuation of a normal spinning operation and, thus, good quality yarn.

As is well-known, however, it is very troublesome to replace aprons, particularly those wrapped around the bottom roller, in conventional spinning frames, due to the structure of the bottom roller. That is, the bottom roller is transversely disposed on the spinning frames along the row of all the spinning units arranged on one side of the spinning frame or along a row of, e.g., six or ten successive units. Provision of such a common bottom roller for a plurality of spinning units makes it unfeasible to replace individual aprons. Therefore, before individual apron wear becomes too severe, all the units common to the bottom roller are stopped and all the aprons common to the bottom roller are replaced. This, however, wastes both time and materials.

The present inventors have previously proposed an improved drafting means having one bottom roller for each one or two spinning units in Japanese Patent Application Nos. 57-92515 and 57-122374.

Though the exchanging operation of the apron is considerably improved by this novel drafting means, there are still some problems which prevent smooth exchange. One is due to the structure of the tenser.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a bottom tenser suitable for use for the above-mentioned novel single or double type bottom roller.

It is another object of the present invention to provide a bottom tenser enabling easy mounting or dismounting of an apron from the bottom roller when an exchanging operation is carried out.

These objects can be achieved by a tenser which has a free end on the same side as that of the bottom roller and which or at least a part thereof is easily displaceable from an operative position so as to attain easy detachment of the apron from the roller. The tenser comprises a body and two guide walls attached to the sides of the body and having projected portions to limit lateral movement of the apron in operation.

The tenser has two aspects: one where it is securable, as a whole, on a stationary part of the spinning frame by an easily detachable fastening means, such as a combination of a screw and a guide groove, and the other wherein the guide wall disposed on the free end side of the tenser is displaceable relative to the body of the tenser from the operative position, which limits the lateral movement of the apron, to its non-operative position, which allows easy detachment of the apron.

Other and further features and advantages of the present invention will be apparent from the following description of the illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained in detail with reference to the accompanying drawings illustrating preferred embodiments, wherein:

FIG. 1 is a front view of a single type bottom roller to which the present invention is applied;

FIG. 2 is a front view of a double type bottom roller to which the present invention is applied;

FIG. 3 is an oblique view of part of a drafting means comprising a combination of a bottom roller, a tenser, and an apron;

FIG. 4A is a sectional front view of a first embodiment according to the present invention;

FIG. 4B is a plan view of the first embodiment shown in FIG. 4A;

FIG. 5A is an oblique view of a second embodiment according to the present invention;

FIG. 5B is a cross-section of a bar of the second embodiment along the I--I plane of FIG. 5A;

FIG. 5C is a sectional side view of the second embodiment showing mounting onto a stand;

FIG. 6 is an oblique view of a drafting means of a fasciated yarn spinning frame to which the second embodiment is applied;

FIG. 7A is a side view of a third embodiment;

FIG. 7B is a sectional view of part of the third embodiment along the II--II plane of FIG. 7A;

FIG. 7C is a sectional view of part of the third embodiment along the III--III plane of FIG. 7A;

FIG. 7D is a development of a keyhole of the third embodiment;

FIG. 8A is a sectional side view of a fourth embodiment;

FIG. 8B is a sectional front view of the fourth embodiment along the IV--IV plane of FIG. 8A;

FIG. 8C is a cross-section of a pin of the fourth embodiment along the V--V plane of FIG. 8B in an enlarged scale;

FIG. 9A is a side view of a fifth embodiment of the present invention;

FIG. 9B is a sectional front view of the fifth embodiment along the VI--VI plane of FIG. 9A;

FIG. 10A is a side view of a sixth embodiment of the present invention;

FIG. 10B is a sectional front view of the sixth embodiment along the VII--VII plane of FIG. 10A;

FIG. 10C is a sectional plan view of the sixth embodiment along the VIII--VIII plane of FIG. 10A;

FIG. 10D is an oblique view of part of a projection of the sixth embodiment;

FIG. 11A is a front view of part of a seventh embodiment of the present invention; and

FIG. 11B is an oblique view of part of the seventh embodiment shown in FIG. 11A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the preferred embodiments, a description will be made of the improved drafting means to which the invention is applied.

FIGS. 1 and 2 show front views of single and double type bottom rollers of the drafting means 1. In the figures, a bottom roller or rollers 2 is or are held on a roller stand or stands 7 in a cantilever manner and driven separately from other rollers by an individual transmission 4 driven by a common driving shaft 3 through a clutch 8. Thus, the roller 2 always has a free end 2a and can rotate or stop irrespective of other rollers or other pairs of rollers. According to this structure, the apron can be exchanged by stopping the problem bottom roller 2 and replacing the damaged apron from the free end 2a.

The operation is explained more clearly by referring to FIG. 3. An apron 5 is wrapped around the bottom roller 2 and is set in tension by a tenser 11. The tenser 11 is also secured on the stand 7 in a cantilever manner so as to have a free end at the same side as the free end 2a of the roller 2. In the exchanging operation, the old apron is slid toward the free end 2a of the roller 2 and is removed therefrom. Thereafter, a new apron is fit on the roller 2 and the tenser 11 in a reverse manner as the removal. A problem, however, has arisen due to the structure of the tenser 11. That is, the tenser 11 has a pair of guide walls 12 on the opposite sides of a body 13. The lower end of the guide wall 12 extends downward to form a projected portion 12a. Accordingly, the apron 5 is prevented from moving laterally during its running by means of the projected portion 12a. However, the projected portion 12a, in turn, obstructs the apron exchanging operation. Since the apron exchanging operation is difficult under this tensioned condition, it is desirable to substantially loosen the apron by displacement of the tenser 11.

The first aspect of present invention will now be explained.

FIGS. 4A and 4B illustrate a first embodiment of a bottom tenser 21 according to the present invention, utilized for a single type bottom roller. The tenser 21 is provided with guide walls 22 projecting downward from both sides of a body 23. A holder 25 extends outward from one end of the body 23. The holder 25 has a two level groove 26 running in from the end of the holder 25 and terminating at the center of the holder 25. A screw 28 is fit in the inside of the groove to secure the tenser 21 on a roller stand 7 of a spinning machine. The width of the upper level of the groove 26 is slightly larger than the diameter of a head 28a of the screw 28 and the width of the lower level of the groove 26 is slightly larger than the diameter of the stem of the screw 28. Further, at the inner end of the groove 26 is provided a recess 29 for accommodating the head 28.

To replace an apron from a bottom roller, the tenser 21 has to be removed from the stand 7. For this purpose, the screw 28 is unscrewed to some extent to free the head 28a from the recess 29, thereby allowing the tenser 21 to be drawn out from the stand 7 along the axis of the bottom roller. Referring back to FIG. 3, since the bottom roller 2 has a free end 2a at one side thereof, the apron 5 would then be removable from the bottom roller 2 through the free end at the same time as the removal of the tenser 21.

As stated before, the tenser 21 can be removed from the stand 7 without completely unscrewing the screw 28. This means, in turn, that the tenser 21 can be set in its position just by engaging the groove 26 of the holder 25 to the screw 28 already half-screwed in its fixed position and, therefore, that the apron can be exchanged in a shorter time.

FIGS. 5A, 5B, and 5C show a second embodiment of a bottom tenser assembly according to the first aspect of the present invention, utilized for a double type bottom roller. The tenser assembly 31 comprises two tensers 31a, 31b each having substantially the same shape as the first embodiment and being secured at the opposite ends of a connecting bar 32.

The tenser assembly 31 is disposed along bottom rollers 2,2 so that each tenser corresponds to a bottom roller 2. The connecting bar 32 is secured on the stands 7. According to the above structure, the tenser assembly 31 cannot be removed by being slid parallel to the bottom rollers 2, 2 as in the case of the first embodiment. For achieving easy detachment from the stands, the bar 32 is of a trapezoidal cross-section, as shown in FIG. 5B, having a longer top side 32a than bottom side whereby a slanted portion 32b is formed on a rear side thereof. On the other hand, on the top wall of each of the stands 7 is provided a recess 33 having a cross-section with a lower portion complementary to that of the bar 32 which is to be disposed so that the slanted portion 32b directs rearward, i.e., toward the bottom roller 2, and with an upper portion wider than the lower portion, both portions being layered so that the front wall of the lower portion is aligned with that of the upper portion but the rear wall of the former is further rearward from that of the latter to form an extended space in the recess 33.

The bar 32 is closely fitted to the lower portion of the recess 33 so that a slanted wall 34 thereof mates with the slanted portion 32b of the bar 32 as shown in FIG. 5C and fixed thereto by screws 38 through apertures 35 of the connecting bar 32.

When removed, the tenser assembly 31 is pulled up from the recess 33 after the screw 38 are completely unscrewed from the stands 7. The slanted portion 32a of the bar 32 can be slid on the slanted wall 34 of the recess 33 into the space of the upper portion of the recess 33, which causes slack of an apron 5. Thereafter, the apron exchanging operation is carried out in the same manner as described before in relation to the first embodiment.

An aspect of the first or second embodiment applied to the fasciated yarn spinning machine is illustrated in FIG. 6. Here, illustration of the top side rollers is omitted so as to show the bottom side parts, especially the middle aprons. A fiber bundle is introduced from the lower side of the drawing through a trumpet 41, and then is attenuated by a back roller 42, a collector 47, apron 5, and a front roller 45 and is finally false-twisted by an air nozzle 46 to form a fasciated yarn. The tenser assembly 31 secured on the stand 7 by means of the screw 38 holds the apron 5 with the aid of a middle roller 43 identical to the above-mentioned bottom roller 2.

Next, a second aspect of the present invention will be explained. In this aspect, the tenser comprises a body and a separate guide wall attached therewith. The guide wall is displaceable from the operative position, whereby the above-mentioned projected portion thereof is substantially eliminated and the apron can be dismounted from or mounted on the tenser while the latter is fixed on the stand.

In FIGS. 7A through 7D, a third embodiment is illustrated. At an outer end of a body 51 of a tenser 50 is projected a key-shaped cylindrical pin 52 with a projection 52a on the circumference thereof. At the corresponding position of a guide wall 55 is provided a keyhole 53 to receive the pin 52. The body 51 is assembled with the guide wall 55 by engaging the pin 52 to the hole 53 and, thereafter, by rotating the guide wall 55 in a predetermined angle about the axis of the pin 52 until the projection 52a is held by a spring 54 provided in the innermost portion 53a of the hole 53. This constitutes the operative position. To dismount the guide wall 55, the guide wall 55 is twisted reversely from the above-stated mounting operation with a torque enabling the projection 52a to overcome the force of the spring 54 until the projection 52a is aligned with the hole 53. In this state, the wall 55 is easily removable from the body 51.

A fourth embodiment is illustrated in FIGS. 8A through 8C, in which a body 61 of a tenser 60 is provided with a cylindrical hole 62 at a center of an outer end thereof and an aperture 63 bored perpendicularly to the hole 62 through a top wall of the body 61. A ball 64 is accommodated in the aperture 63 and is urged into the hole 62 by means of a spring 66. On the other hand, a guide wall 65 has a pin 67 projected from an inner wall thereof at a position corresponding to the hole 62. The pin 67 has an irregularly shaped cross-section at least in part thereof and can be mated with the hole 62. The irregularly-shaped cross-section of the pin 67 constitutes a half circle 67a of the same diameter as the cross-section of the hole 62, an arc 67b of a smaller diameter than the latter, and, in a selected area of the circumference of the pin 67 corresponding to the position of the aperture 63 when engaged, a concave arc 67c to accommodate part of the ball 64.

For assembly, the pin 67 is pushed into the hole 62, taking care that the arc 67b meets with the ball 64 by referring to suitable marks (not shown) on the body 61 and the pin 67. When the pin 67 reaches the ball 64, it therefore pushes the ball 64 back into the aperture 63. The pin 67 can then easily be inserted completely into the hole 62 to reach the innermost portion of the hole 62. The pin 67 is then rotated by twisting the guide wall 65 so that the ball 64 fits into the concave arc 67c. The guide wall 65 is thus fixed to the body 61 by the force of the spring 66 and is maintained in the operative position. Of course, the operation of dismounting the guide wall from the body can be carried out by following the above operation in reverse.

A fifth embodiment is illustrated in FIGS. 9A and 9B, in which a guide wall 75 of a tenser 70 has an insert 71 perpendicularly projected from a surface thereof facing the body 72. The insert 71 is constituted by upper and lower plates 71a and 71b which are formed by folding a strip of resilient material such as spring steel. The rear end of the upper plate 71a is embedded in the guide wall 75 and the rear end of the lower plate 71b is free. The front portion of the upper plate 71a forms a tapered nose 71c mating with the lower plate 71b and the rear portion thereof is flat. At a border between the front and rear portion of the upper plate 71a is provided a step 73, the height of which is less than that of the tapered nose 71c. According to this structure, the thickness of the insert 71 is variable by pressing the lower plate 71b toward the upper plate 71a. On the other hand, the body 72 has, on an outer end thereof, a slit 74 of a rectangular cross-section to receive the insert 71. The height of the slit 14 is larger in an inner part 74b thereof than in an inlet part 74a, whereby a step 76 is formed between the two parts.

For assembly, the insert 71 of the guide wall 75 is pushed into the inlet part 74a of the slit 74 of the body 72. The tapered nose 71c deforms resiliently so that the height of the step 73 matches that of the inlet part 74a. After passing the step 76, the tapered nose 71c returns to its original height. Thus, the guide wall 75 is fixed in its operative position by engagement of the step 73 with the step 76. For removal, the guide wall 75 is slid downward relative to the body 72 so that the nose is decreased in thickness thereof and disengages from the step 76. The guide wall 75 is then pulled out of the body 72.

In FIGS. 10A through 10D is illustrated a sixth embodiment. A body 81 of a tenser 80 has a cylindrical projection 82 on an outer end surface facing a guide wall 85. The projection 82 has two parallel plain surfaces 82a on opposite sides of a stem thereof except for a tip portion 82b. The distance between the plain surfaces 82a is less than the diameter of the tip portion 82b. In turn, the guide wall 85 has an elongated through-hole 83 extending along a longitudinal axis of the guide wall 85. The through-hole 83 is of a double layer structure. An inner layer 87 has a keyhole configuration, while an outer layer 86 has a "race track" configuration. The layers 86 and 87 adjoin each other so that the circular portion of the layer 86 coincides with the circular portion of layer 87 and straight portions thereof overlap. The above coinciding circular portions are disposed at the lowermost end of the hole 83 and constitute an inlet aperture 83a. The inlet aperture 83a has the same diameter as the tip portion of the projection 82. The widths of the straight portions of the outer and inner layers 86, 87 are substantially the same as the diameter of the tip portion 82b and the thickness of the stem portion 82a of the projection 82, respectively. The depths of the outer and inner layers are substantially the same as the heights of the tip portion and the stem portion, respectively.

According to the above structure, for assembly, the projection 82 of the body 81 is inserted into the inlet aperture 83a of the guide wall 85. The guide wall 85 is displaced stably along the through-hole 83 to fit stem portion 82a into the straight portion of the inner layer 87. After the projection 82 reaches the uppermost position of the through-hole 83, the two parts 81 and 85 are prevented from rotating with respect to each other as the stem portion 82 is held by the straight portion of the inner layer 8.

In FIGS. 11A and 11B, a seventh embodiment is illustrated. An upper half of a body 91 of a tenser 90 has a laterally extended portion 91a, on the outer side wall of which there is a groove 92 running from the top wall to the bottom wall. A guide wall 95 is fit in the groove 92 and is supported therein by engaging an elongated hole 94 provided along the longitudinal direction of the guide wall 95 with a pin 93 widthwisely bridging the side walls of the groove 92. In the operative position, the guide wall 95 is fixed in the groove 92 in such a manner that the uppermost end of the hole 94 is held by the pin 93 and the upper half of the guide wall 95 is in frictional contact with the side walls of the groove 92, while the lower half of the guide wall 95 is downwardly projected from the groove 92. The projected portion of the wall 95 forms a stopper for lateral movement of the apron in operation, as stated before. The guide wall 95 is upwardly slidable along the groove 92, while being guided by the pin 93 and the elongated hole 94.

When exchanging the apron, the wall 95 is slid upward so that the lowermost end of the elongated hole 94 abuts the pin 93. An inner edge 95a of the lowermost end of the guide wall 95 facing the body 91 has been rounded off to allow clockwise rotation when the lower end of the hole 94 reaches the pin 93. Thus, the guide wall 95 can be turned outward just at a right angle and be held in the position by engagement of the lower end thereof to the bottom of the groove 92, as shown by chain lines in FIG. 11B. As a result, the projected portion of the guide wall 95 is eliminated, making the apron easily replaceable.

As stated above, according to the first aspect of the present invention, the tenser can easily be mounted or dismounted, allowing replacement of an apron can be completed in a shorter time.

Further, according to the second aspect, as the guide wall can be displaced relative to the body of the tenser, the apron can be replaced without being obstructed by the projected portion of the tenser, while the tenser is fixed to the stand.

Thus, the machine stoppage time for a spinning frame is drastically decreased and the resultant yarn quality is improved. 

We claim:
 1. A tensioning device for tensioning an apron wrapped around a cantilever-mounted bottom roller of a drafting means in a spinning frame, said roller having an outer free end on one side from which said apron may be removed, said tensioning device being adapted to be mounted in juxtaposition with said roller so that said apron may be installed on and removed from said tensioning device on an access side of said tensioning device adjacent the free end of said roller, said tensioning device comprising:a cantilever-mountable body having an apron-supporting surface and a free end on the access side; a guide wall member connected to said body at said free end thereof and having a projection for preventing lateral movement of said apron toward said free end of said body when said projection is in a usage position, said guide wall member being movable with respect to said body to move said projection to an apron removal position so as to permit lateral movement of said apron over said free end of said body; and connecting means for mechanically locking said guide wall member to said body to prevent movement of said guide wall member laterally of said body when said projection is in said usage position,said connecting means permitting movement of said guide wall member relative to said body, to said apron removal position wherein said apron may be removed from or installed on the free end of said tensioning device.
 2. A tensioning device according to claim 1, wherein said connecting means is a combination of a protrusion projected in the lateral direction and a bore receiving the protrusion, each being provided at either of said body or guide wall member of said tensioning device, and said guide wall member is rotatable in a plane parallel to a side surface of said body around the axis of said connecting means from its operative position to a non-operative position.
 3. A tensioning device according to claim 1, wherein said connecting means is a combination of a protrusion projected in the lateral direction and a bore receiving the protrusion, each being provided at either of said body or guide wall member of said tensioning device, and said guide wall member is detachable from said body by disengagement of said protrusion from said bore.
 4. A tensioning device according to claim 1, wherein said guide wall member is received in a groove provided on a side surface of said body and held therein by engagement of an elongated through-hole of said groove with a pin provided in an upper portron of said groove for bridging inner walls of said groove, whereby said guide wall member is displaceable along said groove and is in said usage position at the lowermost displacement thereof and in said apron removal position at the uppermost displacement where said guide wall is rotatable in a plane perpendicular to a side surface of said body around said pin.
 5. A tensioning device for tensioning an apron wrapped around a cantilever-mounted bottom roller of a drafting means in a spinning frame, said roller having an outer free end on one side from which said apron may be removed, said tensioning device being adapted to be mounted in juxtaposition with said roller so that said apron may be installed on and removed from said tensioning device on an access side of said tensioning device adjacent the free end of said roller, said tensioning device comprising:a cantilever-mountable body having an apron-supporting surface and a free end on the access side; a guide wall member connected to said body at said free end thereof and having a projection for preventing lateral movement of said apron toward said free end of said body when said projection is in a usage position, said guide wall member being movable with respect to said body to move said projection to an apron removal position so as to permit lateral movement of said apron over said free end of said body; and connecting means for mechanically locking said guide wall member to said body to prevent movement of said guide wall member laterally of said body when said projection is in said usage position,said connecting means comprising a key-shaped cylindrical pin extending from said body, and a mating keyhole in said guide wall, said connecting means permitting movement of said guide wall member relative to said body, to said apron removal position wherein said apron may be removed from or installed on the free end of said tensioning device, said pin and keyhole of said connecting means cooperating to permit rotation of said guide wall member relative to said body between said usage position and said apron removal position, said guide wall member being removable from said body when said guide wall member is in the apron removal position thereof.
 6. The tensioning device according to claim 5, further comprising spring means disposed within said keyhole for retaining said guide wall in said usage position.
 7. A tensioning device for tensioning an apron wrapped around a cantilever-mounted bottom roller of a drafting means in a spinning frame, said roller having an outer free end on one side from which said apron may be removed, said tensioning device being adapted to be mounted in juxtaposition with said roller so that said apron may be installed on and removed from said tensioning device on an access side of said tensioning device adjacent the free end of said roller, said tensioning device comprising:a cantilever-mountable body having an apron-supporting surface and a free end on the access side; a guide wall member connected to said body at said free end thereof and having a projection for preventing lateral movement of said apron toward said free end of said body when said projection is in a usage position, said guide wall member being movable with respect to said body to move said projection to an apron removal position so as to permit lateral movement of said apron over said free end of said body; and connecting means for mechanically locking said guide wall member to said body to prevent movement of said guide wall member laterally of said body when said projection is in said usage position,said connecting means comprising a shaft extending from said guide wall member, and a hole in said body for rotatably receiving said shaft, said connecting means including spring-loaded detent means mounted on said body and acting on said shaft for permitting removal of said guide wall member from said body, wherein said apron may be removed from or installed on the free end of said tensioning device.
 8. A tensioning device for tensioning an apron wrapped around a cantilever-mounted bottom roller of a drafting means in a spinning frame, said roller having an outer free end on one side from which said apron may be removed, said tensioning device being adapted to be mounted in juxtaposition with said roller so that said apron may be installed on and removed from said tensioning device on an access side of said tensioning device adjacent the free end of said roller, said tensioning device comprising:a cantilever-mountable body having an apron-supporting surface and a free end on the access side; a guide wall member connected to said body at said free end thereof and having a projection for preventing lateral movement of said apron toward said free end of said body when said projection is in a usage position, said guide wall member being movable with respect to said body to move said projection to an apron removal position so as to permit lateral movement of said apron over said free end of said body; and connecting means for mechanically locking said guide wall member to said body to prevent movement of said guide wall member laterally of said body when said projection is in said usage position,said connecting means comprising a hole in said body having a shoulder therein, and a resilient insert attached to said guide wall and extending into said hole so that a portion of the insert abuts said shoulder to prevent lateral movement of said guide wall away from said body, said insert being resiliently deformable upon movement of said guide wall transversely of said free end of said body, to disengage said insert portion from said shoulder so that said guide wall member can be removed from said body.
 9. A tensioning device for tensioning an apron wrapped around a cantilever-mounted bottom roller of a drafting means in a spinning frame, said roller having an outer free end on one side from which said apron may be removed, said tensioning device being adapted to be mounted in juxtaposition with said roller so that said apron may be installed on and removed from said tensioning device on an access side of said tensioning device adjacent the free end of said roller, said tensioning device comprising:a cantilever-mountable body having an apron-supporting surface and a free end on the access side; a guide wall member connected to said body at said free end thereof and having a projection for preventing lateral movement of said apron toward said free end of said body when said projection is in a usage position, said guide wall member being movable with respect to said body to move said projection to an apron removal position so as to permit lateral movement of said apron over said free end of said body; and connecting means for mechanically locking said guide wall member to said body to prevent movement of said guide wall member laterally of said body when said projection is in said usage position,said connecting means comprising (i) a cylindrical projection extending from said body, said projection comprising a stem having a free end, and two parallel flat surfaces on opposite sides of the stem, said flat surfaces ending at a tip portion of the stem adjacent the free end thereof, and (ii) an elongated through-hole extending along a longitudinal axis of the guide wall, said through-hole having a double-layer structure, with an inner layer having a keyhole configuration and an outer layer having a race track configuration, said layers adjoining each other and having coinciding circular portions and overlapping straight portions, said connecting means preventing rotational movement of said guide wall member relative to said body in said usage position, and permitting movement of said guide wall member relative to said body along the longitudinal axis of the guide wall member, to said apron removal position wherein said apron may be removed from or installed on the free end of said tensioning device by rotating the guide wall member.
 10. A tensioning device for tensioning an apron wrapped around a cantilever-mounted bottom roller of a drafting means in a spinning frame, said roller having an outer free end on one side from which said apron may be removed, said tensioning device being adapted to be mounted in juxtaposition with said roller so that said apron may be installed on and removed from said tensioning device on an access side of said tensioning device adjacent the free end of said roller, said tensioning device comprising:a cantilever-mountable body having an apron-supporting surface and a free end on the access side; a guide wall member connected to said body at said free end thereof and having a projection for preventing lateral movement of said apron toward said free end of said body when said projection is in a usage position, said guide wall member being movable with respect to said body to move said projection to an apron removal position so as to permit lateral movement of said apron over said free end of said body; and connecting means for mechanically locking said guide wall member to said body to prevent movement of said guide wall member laterally of said body when said projection is in said usage position,said connecting means comprising (i) a transversely extending groove in the free end of said body, with a pin traversing oppositely disposed wall of said groove, and (ii) an elongated hole extending longitudinally of said guide wall member, with said pin extending through said hole to permit longitudinal movement of the guide wall member while preventing lateral movement of the guide wall member in the usage position thereof, said connecting means preventing rotational movement of said guide wall member relative to said body in said usage position, and permitting movement of said guide wall member relative to said body along the longitudinal axis of the guide wall member, by sliding of said pin along said elongated hole, to said apron removal position wherein said apron may be removed from or installed on the free end of said tensioning device by rotating the guide wall member, said guide wall member having a rounded edge portion permitting such rotation by providing clearance with respect to an adjacent surface of said groove in said apron removal position. 